Well, they are not the hardiest fish, I guess they are kinda difficult, but in the end its worth the work. They are so cool! Just DON'T overstock! They are really aggressive! Also, If you decided against the DPs, you could do a pair of blue rams!

I was thinking on just having a pair in the tank by themselves. How do determine the gender of the puffer? Any good websites that have good information on dwarf puffer care? I do not want to set up the tank until I am fully read up on their care and such, but how aged does the tank need to be? I will problably get the puffer pair about 3-4 months from now maybe longer so should I set it up now and let the tank age maybe with a few guppies or something?

You could set up a pretty sizable colony of dwarf puffers in a 20L, maybe five or six of them. The substrate doesn't matter much although sand is better (for easier hunting). Lots of plants and driftwood and/or rocks to break up the lines of sight and create territories. You could add a bristlenose pleco or two to take care of algae, so long as you had some driftwood in the tank. They can be picky eaters so be prepared to feed them live foods (although many will eat frozen foods like bloodworms). A source of live blackworms is good, and it'd be a good idea to have a breeding colony of pond snails in another tank as these are pretty much the staple diet of dwarf puffers.